Method and device for desalination of water and removal of carbon dioxide from exhaust gases

ABSTRACT

This invention relates to a method for desalination of seawater ( 5, 30 ) and separation of CO 2  from exhaust ( 77 ) from a gas turbine ( 7 ). LNG ( 4 ) is fed into a heat exchanger ( 6 ) in which it receives heat from seawater ( 5 ) and heat from steam ( 27 ) from an exhaust boiler, and heat from combustion air ( 3 ) via a line to an air inlet ( 33 ) of said gas turbine ( 7 ), for evaporating LNG ( 4 ) to gas which is fed to a gas export module ( 10 ) and to a fuel gas skid ( 8 ) for supplying said gas turbine ( 7 ) with fuel. Thus said combustion air ( 3, 28 ) at the air inlet to said gas turbine ( 7 ) obtains a lowered temperature and increases an efficiency of said gas turbine ( 7 ). Said CO 2 -rich exhaust gas ( 77 ) from said gas turbine ( 7 ) is fed into a process unit ( 17 ) having an inlet ( 35   a ) with a fan ( 35   b ) and an outlet for CO 2 -reduced exhaust ( 13 ). Said cooled seawater from said heat exchanger ( 6 ) is fed into said process unit ( 17 ) via a coaxial feed pipe ( 67 ) for seawater and NH 4 OH arranged in said process unit ( 17 ). NH 4 OH is fed into said coaxial feed pipe ( 67 ) and is then mixed with said cooled seawater ( 30 ) and released via a series of nozzles in several vertical levels from said feed pipe ( 67 ) to said process unit&#39;s ( 17 ) upwards flowing, rotating exhaust ( 77 ). By this device a good mixture of NH 4 OH—containing salt water and CO 2 -rich exhaust is achieved, for formation of NaHCO 3 , NH 4 Cl, and fresh water.

The invention relates to an improved process for removal of CO₂ fromexhaust gases, in which huge amounts of seawater are transformed tofresh water by addition of ammonia NH₃ with subsequent precipitation ofsodium hydrogen carbonate NaHCO₃ and ammonium chloride NH₄Cl. Theprocess is made more efficient by using air, seawater and steam as heatsources during evaporation of liquefied natural gas (LNG). Cooled air isprovided for the air inlet of a gas turbine, a feature that considerablyimproves the efficiency. Cooled seawater is used for removal of CO₂ fromthe exhaust gas from the gas turbine. This process is made moreefficient by having a low seawater temperature; about 10° C. Steam isgenerated in the exhaust boiler of the gas turbine. The gas turbinegenerates electrical power for running the process that is necessary forevaporation of LNG. The excess electrical power is exported.

KNOWN ART IN THE FIELD

Precipitation of NaHCO₃ and NH₄Cl as described above is, in its basicprinciple, known as the Solvay soda process, which has been industriallydominating for a long time. Further we refer to U.S. Pat. No. 6,180,012describing a closed tank in which enters CO₂-rich exhaust and seawater(with NaCl) and in which separately ammonia NH₃ is injected, and freshwater is formed. Sodium hydrogen carbonate NaHCO₃ and ammonium chlorideNH₄Cl precipitate to the bottom and are separated from seawater, whichis transformed to fresh water.

It may be inefficient not to mix salt water and ammonia NH₃ before theinjection into the chamber, as the process described in U.S. Pat. No.6,180,012, because the components NH₃ and NaCl may not have sufficienttime to be effectively mixed before further reaction with CO₂ in theexhaust gas. Further, it is a disadvantage of the U.S. Pat. No.6,180,012 that the injection takes place only in a limited upper portionof the tank, and not a more thorough mixing, e.g. in a more extensiveportion of the tank. It is a further disadvantage of the U.S. Pat. No.6,180,012 that the process takes place with inlet of an exhaust gas to aclosed tank, because the closed tank will form a counter pressureagainst the outlet from the gas turbine, and thus there is a risk of aconsiderable reduction of the gas turbine efficiency.

A typical gas turbine of 25 Megawatt (MW) generates an exhaust flow ofabout 3,3 kg/s of CO₂. That represents a large and undesirableproduction of CO₂ considering the probable contributions to greenhouseeffects on the global atmosphere. Further, we expect that the unifiedprocess according to the invention also will prove commercially healthybecause several countries may incur official CO₂-fees and/or trade CO₂emission permissions, so-called “green certificates”.

The process according to a preferred embodiment of the invention has itsgreatest potential in those parts of the world in which there is a lackof fresh water, e.g. in the Middle East, Western Africa, The Read Sea,etc. One of the main purposes of the invention is to contribute to theuse of liquefied natural gas (LNG), seawater and ammonia for anelectricity production of significantly reduced CO₂-emission, andevaporation of LNG simultaneously with soda production and fresh waterproduction, in which all the products have a sales value. Consideringthat the invention also improves the efficiency of the electricityproduction from the gas turbine, by cooling the air to the gas turbineby means of LNG, the invention represents an essential improvement forefficient use of the Solvay process. Further, the process is dependentof low sea water temperature in order to achieve efficient removal ofCO₂, about 10° C. There is a potential incompatibility in the facts thatthe seawater temperatures rarely are low in those coastal areas of theworld in which there is a lack of fresh water for agricultural purposesor alternatively industrial purposes. Further, there is a potentialincompatibility in the facts that evaporation of LNG requires a highseawater temperature, whereas the removal of CO₂ requires a low seawatertemperature. The preferred embodiment of the present invention aims atcombining these seemingly counteractive effects, thereby creating animproved process that should be commercially applicable and having alarge market potential, particularly in those areas mentioned above.

An article called “Chemical Separation Process for Highly SalineWater, 1. Parametric Experimental Investigation” in Ind. Eng. Chem.Res., 1996, 35, 799-804, describes the separation of highly salinewaters under varius contitions and is carried out using apartial-desalting process. The method utilizes a series of chemicalreactions involving conversion of Sodium Cloride, the major constituentin saline waters, into sodium bicarbonate, which precipitates under theexperimental conditions, and ammonium chloride, which can be separatedby crystallization. Experiments of absorption of carbon dioxide in anammoniated brine have demonstrated the efficiency of the method.

SUMMARY OF THE INVENTION

The invention is a method for desalination of salt water, preferablyseawater, and separation of CO₂ from a CO₂-rich exhaust gas from a fuelcombustion engine or gas turbine, comprising the following steps:

-   -   LNG is fed into a heat exchanger in which heat is taken from        seawater and heat from steam from a steam turbine, and heat from        combustion air via a line to the air inlet to a gas turbine, for        evaporating LNG to gas being fed to a gas export module and to a        fuel gas skid for providing the gas turbine with fuel;    -   In which the combustion air, which at the air supply to the gas        turbine thus has a lowered temperature, and thus increases the        efficiency of the gas turbine;    -   In which CO₂-rich exhaust gas from the gas turbine is led into a        chamber or process unit having an inlet with a fan and an outlet        for CO₂-removed exhaust;    -   In which the cooled salt water from the heat exchanger is fed        into the process unit via an upper swivel having vanes that        rotates a coaxial feed pipe for seawater and NH₄OH, said coaxial        pipe being arranged preferably in a centre line in said process        unit;    -   In which NH₄OH is fed in via a lower swivel of said insert        coaxial pipe and mixed and released with the cooled salt water a        series of nozzles at several vertical levels from the coaxial        pipe to the upwards streaming and rotating exhaust through the        process unit, in order to achieve a good mixture of        NH₄OH-containing salt water and CO₂-rich exhaust, for formation        of NaHCO₃, NH₄Cl, and H₂O.

The invention is also a process unit for removing CO₂ from an exhaustfrom a combustion engine or gas turbine, comprising the followingfeatures:

-   -   an inlet with a fan and an outlet for exhaust of reduced CO₂        content;    -   in which cooled salt water can be piped into said process unit        via an upper swivel having vanes for rotating a coaxial pipe,        said coaxial pipe for seawater and NH₄OH feed, said coaxial feed        pipe being arranged preferably in a centre line of said process        unit;    -   in which NH₄OH can be guided in via a lower swivel on said        coaxial pipe and mixed with said cooled salt water and released        via a series of nozzles from said feed pipe, said nozzles        arranged in several vertical levels, to upwardly flowing and        rotating exhaust of said process unit;    -   thus for achieving a mixture of NH₄OH-containing salt water and        CO₂-rich exhaust for formation of NaHCO₃, NH₄Cl and desalinated        water.

FIGURE CAPTIONS

Attached are figure drawings made for illustrating a preferredembodiment of the invention. However, the figure drawings are not meantfor being construed as limiting to the invention, which shall be limitedby the attached claims only.

In the drawing figures is used a partially converted petroleum oiltanker as process unit. It is not a condition to the invention that suchconverted tankers are used, but second hand tankers are cheap andentirely useful under protected conditions, e.g. in an import harbourfor LNG for which one requirement may be a protected harbour.

FIG. 1 illustrates a plan section of the terminal limits or process area26, and illustrates in-flowing fluids and dry matter to the process fromthe left side in the drawing, with products from the products at theright side in the drawing. From the left side are illustrated in-flowingfluids and dry components as follows: Chalk Ca(OH)₂ (1) is sent to theprocess unit for regenerating of ammonia NH₃ (19), which will beexplained below. Ammonia (2) is sent to a mixing unit for seawater andammonia, for formation of NH₄OH for injection via an insert feed pipe(67) to a process unit (17) for removal of CO₂ from exhaust gas (77)from a gas turbine (7), resulting in release of cleaned exhaust gas (13)to the atmosphere. Central for the preparation to the process is one ormore heat exchangers (6). Combustion air of ambient temperature, e.g.20-35° C., is led into the heat exchanger. Liquefied natural gas (LNG)(4) from an LNG-storage tank (80) outside of the system, is piped intothe heat exchanger (6) while having a temperature of about −163° C. LNG(4) receives heat from the combustion air (3), and from seawater (5) andfrom steam from the exhaust gas steam boiler (18), steam of which isalso piped through the heat exchanger. The paths of those fluids throughthe heat exchanger are better illustrated in FIG. 1. Boil-off gas (73)from the storage tank (80) may also be guided in through the heatexchanger if heating is needed before it is fed into the gas skid module(8) to constitute fuel for the gas turbine (7). Possible excess boil-offgas (73) may be fed into a line (29) to a gas export module (10).

The heat exchanger (6) is arranged before the gas turbine (7) and theprocess unit (17) constituting an exhaust process tower (17) foradsorbing CO₂ from the exhaust, leading further to a precipitationprocess unit for fresh water at the right side of the drawing.

The process is, according to a preferred embodiment, a method fordesalination of salt water (5), which may be seawater or brackish water,with separation of CO₂ from a CO₂-rich exhaust (77) from a combustionengine, boiler or gas turbine (7). The process comprises the followingsteps:

LNG (4) is fed into the heat exchanger (6) in which it receives heatfrom the seawater (5) and heat from steam (27) from a steam turbine(31), and also heat from combustion air (3) sent via a line (28) to theair inlet (33) to the gas turbine (7). LNG (4) will then receive heatand evaporate to gas (29) that is led to a gas export module (10) and toa fuel gas skid (8) for providing the gas turbine (7) with fuel. Thecombustion air (28) at the air inlet (33) to the gas turbine (7) therebyis lowered in temperature out of the heat exchanger due to being cooleddown by LNG (4), and thus increases the efficiency of the gas turbine(7).

CO₂-rich exhaust gas (77) from the gas turbine (7) is led into a chamberrather called a process unit (17) having an inlet (35 a) provided with afan (35 b) in the lower portion of the process unit (17), and an outlet(74) for CO₂-removed exhaust (13) at the upper end of the process unit(17).

The cooled salt water (30) from the heat exchanger (6) is fed into theprocess unit (17) via an upper swivel (40) having vanes that rotate aninsert coaxial pipe (67) for seawater and NH₄OH in a desired direction(71) being opposite of the desired rotation direction (72) for theexhaust gas, and preferably being arranged along the centre line insidethe process unit (17). This increases the degree of mixing between theseawater mixture and the exhaust gas considerably compared to the U.S.Pat. No. 6,180,012.

NH₄OH is led in through a lower swivel (46) on the coaxial pipe (67).NH₄OH is mixed with the cooled salt water (30) and flushed out into theprocess unit (17) via a series of radially directed nozzles (42) atseveral vertical levels from the coaxial pipe (67) to the upwardlyflowing, rotating exhaust (77) through the process unit (17). As theexhaust (77) is reduced in CO₂ during the continuous chemical process,we name it CO₂-lean exhaust (13). By means of the rotating nozzles andthe oppositely rotating exhaust, a good mixing of NH₄OH-rich salt waterand CO₂-rich exhaust (77) is achieved, for formation of NaHCO₃, NH₄Cl,and H₂O.

According to a preferred embodiment of the invention the process unit(17) has a diameter increasing with increased elevation from the lowerinlet (35 a) to the upper outlet (74). Drain gutters (38) to drains (43)are arranged, leading to outlets (45) to a collecting tank (48) forNaHCO₃, NH₄Cl, and fresh water.

According to a preferred embodiment of the invention, which differsessentially from the mentioned U.S. Pat. No. 6,180,012 is an exhaust fan(35B) forcing forward the exhaust (77) and thus reduces the counterpressure for the gas turbine (7) so as to compensate the pressure dropthrough the process unit (17) in order to maintain the efficiency of thegas turbine. The exhaust fan (35B) initiates at the same time a rotationof the exhaust gas (77), further reinforced by means of fixed guidevanes (36) arranged downstream at the inlet (35 a) of the process unit(17).

According to the preferred embodiment of the invention NH₄OH entersthrough the lower swivel (46) to a central coaxial inner pipe (47) inthe coaxial feed pipe (67) in the process unit (17). The inner pipe (47)is surrounded by a mantle of salt water (30) through which NH₄OH is ledout through pipes to sea water ring nozzles (42) in the feed pipe (67).In the nozzles (42) NH₄OH and seawater are mixed through flushing fromthe nozzles to the CO₂-rich exhaust (77) gradually being changed toCO₂-lean exhaust (13) on its way upward through the process unit (17).The nozzles are preferably provided with NH₄OH-radial distributors (70)arranged just outside the nozzles (42) in order for NH₄OH to be forcedout through an enveloping flow of the mixed cooled seawater (30).

This implies two essential advantages relative to U.S. Pat. No.6,180,012 in that ready-mixed droplets of NH₄OH are flushed out towardsthe NaCl-molecules and contribute to weaken the molecular bindingbetween Na and Cl, thus facilitating formation of NaHCO₃ as one of theend products.

Precipitated material of NaHCO₃, NH₄Cl intermediately dissolved in H₂Oare conducted to a precipitator (22) for separation of NaHCO₃ and NH₄Clfrom the water H₂O which is generally pure fresh water if the process isthoroughly controlled and low temperature of the seawater is maintained.

According to a preferred embodiment of the invention the precipitator(22) is vertically standing and cylindrical, and has a rotation-inducingtangential inlet (25B) for NaHCO₂/NH₄Cl dissolved in water. The drivingpressure is generated from the pressure head from the collector tank(48) to the inlet (25B). NaHCO₂/NH₄Cl is precipitated by the rotationand the gravitation towards the bottom of the precipitator (22).

According to a preferred embodiment of the invention fresh water (74) istaken out through a fresh water overflow pipe (75) to a fresh waterfilter tank (62). The fresh water (74) from the filter tank (62) is sentthrough a filter (61) to a distribution- and settling tank (60). Saltwater may be present at the bottom of the settling tank (60), of whichsalt water may be lifted back to the seawater pipe (30) by means of thepump (53). Fresh water (74) is pumped by means of the pump (54) tostorage tank (59), and further from storage tank (59) via discharge pump(58) and booster pump/export pump (56) to an export pipeline (14).

The precipitated NH₄Cl and NaHCO₃ is lifted by means of a screw pump or“archimedes screw” (51) that is driven by a motor (50), to an outlet(76) from the precipitator (22) to a refining process compartment (64).Chalk Ca(OH)₂ (1) is led into the process unit (20) for regeneration ofammonia NH₃ that is fed via a pipe (19) to be mixed with additional NH₃(2) from the ammonia tank (65). The ammonia (2, 19) is led further tothe mixing unit (32) mixing salt water and ammonia (2, 19) and pumps themixture NH₄OH into the feed pipe (67) in the process unit (17).

According to a preferred embodiment of the invention, the gas turbine(7) drives a generator (9) for generating electrical energy thatpartially may be exported as energy (15), and partially to be used forpumping work, gas and/or CO₂ export work, and heating a process unit(24) that precipitates soda/Na₂CO₃ (12) for export, and CO₂ and freshwater, which are exported or returned to the process.

Components List

-   1 Ca(OH)₂—limestone-   2 NH₃—ammonia-   combustion air to gas turbine(s), e.g. 20° C. before the heat    exchanger, and after the heat exchanger in to the gas turbine    holding 5° C.-   4 liquefied natural gas (LNG), −163° C., (1,2 mill. tons/year.-   5 seawater—250 000 m3/day, e.g. 15° C. in to the heat exchanger, and    about 5° C. out from the heat exchanger, and further to the rotating    feed pipe (67)-   6 heat exchanger, (possibly several in parallel).-   7 gasturbine(s), (120 MW)-   8 gas skid module, for treating gas supply to the gas turbine,    (pressurizing, drying and filtering)-   9 generator-   10 gas export module (needs 25 MW power to deliver 131 MSC FTD    (Mill. dard Cubic Ft./day (evaporated) LNG/year)-   11 CaCl₂—drying agent-   12 Na₂CO₃—soda-   13 exhaust out of the process, low in CO₂—contents-   14 fresh water about 250000 m³/day-   15 electrical energy for export.-   16 gas export from the gas export gas export module 10-   17 process unit, for adsorption of CO₂ from exhaust-   18 exhaust boiler from turbine 7 for generating steam-   19 regenerated NH₃—ammonia-   20 process unit for regenerating NH₃-   21 ammonium chloride solution NH₄Cl-   22 process unit for precipitation of sodium hydrogen carbonate    NaHCO₃ and ammonium chloride NH₄Cl from water-   23 sodium hydrogen carbonate NaHCO₃-   24 process unit for precipitation of soda Na₂CO₃.-   25 NaHCO₃ and NH₄Cl—solution pipe-   25B tangential inlet to process unit (22) for precipitation-   26 terminal border (extent of the area)-   27 steam to heat exchanger (condenser)-   28 combustion air to gas turbine (see (3)), about 5° C.-   29 gas to gas export module 10 and to fuel gas skid 8-   30 seawater to process unit cooled to about 5° C. out from heat    exchanger 6-   31 steam turbine-   32 mixer for seawater and ammonia NH₃-   33 air inlet to gas turbine-   34 muffler (sound attenuator) out from gas turbine-   35A inlet to process unit (17) from exhaust fan (35 b)-   35B exhaust fan-   36 exhaust lead vanes for reinforcing rotation of exhaust gas (77)    of high CO₂-contents-   37 drain at lower portion of the process unit (17)-   38 guide gutter to drain (43)-   39 horizontal and vertical bearing for the rotating coaxial pipe    (67)-   40 swivel for injection of cooled sea water (30), with guide vanes    for rotating the insert feed pipe (67)41 support beams (3 ex) for    the feed pipe (67)-   41 support beams (3 ex) for the coaxial pipe (67)-   42 nozzles for NH₄OH and seawater-   43 drain from guide gutter (38)-   44 horizontal bearing for the rotating feed pipe (67)-   45 drop line from the drain (43) to the collector tank (48) for    NaHCO₃ and NH₄Cl—solution-   46 swivel for NH₄OH solution-   47 supply line for NH₄OH to swivel (46) with rotating coaxial pipe    (67) with nozzles (42)-   48 collecting tank for NaHCO₃ og NH₄Cl—solution (25)-   49 choke valve at outlet form collector tank (48)-   50 motor for screw (archimedes screw) on lift pump (51)-   51 screw lift pump-   52 cofferdam between tanks-   53 lift pump for salt-containing water from bottom portion of the    distribution/settling tank (60).-   54 lift pump for fresh water from distribution/settling tank (60) to    fresh water age tank (59)-   55 main deck of (converted) crude oil tanker-   56 export booster pump (s) for fresh water-   57 pump compartment-   58 discharge pump, pressure support to export pump (56)-   59 fresh water storage tank-   60 distribution tank/settling tank-   61 filter between filter tank (62) and distribution/settling tank    (60)-   62 filter tank-   63 drain from precipitation process unit (22)-   64 process compartment for precipitated material (76)-   65 tank for NH₃ ammonia-   66 bottom of (converted) crude oil tanker-   67 rotating coaxial feed pipe for NH₄OH and seawater-   68 ring nozzle for sea water (30) in rotating coaxial pipe (67)-   69 nozzles for NH₄OH on pipe from coaxial supply line (47) in the    rotating coaxial pipe (67) in the process unit (17)-   70 radial distributor for NH₄OH outside of the nozzle (69)-   71 rotation direction for the coaxial pipe (67)-   72 rotation direction for the exhaust (77)-   73 boil-off gas from 1 ng storage tank-   74 fresh water from the distribution/settling tank (60)-   75 overflow pipe for water from the separation/process unit (22)-   76 outlet of precipitated material sodium hydrogen carbonate NaHCO₃    and ammonium chloride NH₄Cl-   77 exhaust having a hich CO₂—content, in to the process unit (17)    from the gas turbine (7)-   78 lift pump from the tank (65) which delivers to the mixer (32)-   79 turbulence attenuating ribs-   79A outlet for exhaust removed of CO₂-   80 LNG storage tank outside the process plant

1. A method for desalinating salt water (5), preferably sea water, andfor removing CO₂ from a CO₂-rich exhaust (77) from a combustion engineor gas turbine (7), comprising the following steps: LNG (4) is fed intoa heat exchanger (6) in which said LNG (4) receives heat from thefollowing sources: said salt water (5) that becomes cooled salt water(30); and steam (27) generated from a steam turbine (31); and combustionair (3) from the atmosphere, which is provided via a line (28) to an airinlet (33) of said gas turbine (7); said heat exchanger (6) evaporatingsaid LNG (4) to gaseous form (29), said gas (29) being guided to a gasexport module (10); and to a fuel gas skid (8) for supplying fuel tosaid gas turbine (7); in which said combustion air (3, 28) which, atsaid air inlet (33) to said gas turbine, has a lowered temperaturerelative to said combustion air (3) and thus increases the efficiency ofsaid gas turbine (7); in which CO₂-rich exhaust (77) from said gasturbine (7) is guided into a process unit (17) having an inlet (35 a)with a fan (35 b) and an outlet (79 a) for exhaust (13) of reduced CO₂content; in which said cooled salt water (30) from said heat exchanger(6) is conveyed into said process unit (17) via an upper swivel (40)having vanes for rotating a coaxial pipe (67), said coaxial pipe (67)for distributing seawater and NH₄OH feed, said coaxial feed pipe (67)being arranged preferably in a centre line of said process unit (17); inwhich NH₄OH is fed via a lower swivel (46) on said coaxial pipe (67) andmixed with said cooled salt water (30) and released via a series ofnozzles (42) from said feed pipe (67), said nozzles (42) arranged inseveral vertical levels, to upwardly flowing and rotating exhaust (77)of said process unit (17); thus achieving a mixture of NH₄OH-containingsalt water and CO₂-rich exhaust (77) for formation of NaHCO₃, NH₄Cl anddesalinated water.
 2. The method according to claim 1, wherein saidprocess unit (17) has an increasing diametre with increasing elevationfrom said lower inlet (35 a) to said upper outlet (79 a), and withdraining guide gutters (38) to drains (43) leading to outlets (45) andfurther to a collector tank (48) for the process unit's (17) productsNaHCO₃, NH₄Cl and fresh water.
 3. The method of claim 2, wherein saidexhaust fan (35 b) reduces a counter pressure on said gas turbine (7) sothat a pressure drop through said process unit (17) is compensated so asto maintain an efficiency of said gas turbine (7).
 4. The method ofclaim 3, wherein said exhaust fan (35 b) starts a rotation in saidexhaust gas (77), said rotation being reinforced by fixed guide vanes(36) arranged after said inlet (35 a) to said process unit (17).
 5. Themethod of claim 1, wherein said rotation direction of said exhaust (77)and said rotation direction of said coaxial feed pipe (67) are madeopposite in order to increase a degree of mixing between exhaust (77)and added fluid (30, 47).
 6. The method according to claim 1, whereinNH₄OH enters through said lower swivel (46) to a central, coaxial innerpipe (47) in said coaxial feed pipe (67), said inner pipe (47) beingsurrounded by a mantle of salt water (30) and in which inner pipe (47)NH₄OH is guided out through pipes (69) to seawater ring nozzles (42) ofsaid feed pipe (67), for mixing of NH₄OH and seawater in said nozzles(42) during flushing of said NH₄OH and said seawater from said nozzles(42), so as to change said exhaust (77) which gradually changes toCO₂-lean exhaust (13).
 7. The method according to claim 6, preferablywith an NH₄OH-radial distributor (70) arranged just outside said nozzles(42).
 8. The method of claim 1, wherein precipitated material of NaHCO₃,NH₄C₁ and H₂O are guided to a precipitator (22) for separating H₂O fromNaHCO₃ and NH₄Cl.
 9. The method of claim 8, wherein said precipitator(22) is vertically cylindric, having a tangential inlet (25 b) for saidNaHCO₃/NH₄Cl solution to be precipitated by rotation and gravity towarda bottom of said precipitator (22).
 10. The method according to claim 9,wherein fresh water is let out through a fresh water overflow pipe (75)to a fresh water and filter tank (62).
 11. The method according to claim10, wherein said fresh water (74) from said filter tank (62) is allowedto pass through a filter (61) to a distribution tank/settling tank (60).12. The method of claim 10, wherein salt containing water from a bottomof said settling tank (60) is lifted back to a seawater pipe (30) usinga pump (53).
 13. The method of claim 11, wherein fresh water (74) ispumped by means of a pump (54) to a storage tank (59), and further fromsaid storage tank (59) via a discharge pump (58) to a booster or exportpump (56) to an export pipeline (14).
 14. The method of claim 9, whereinsaid precipitated NH₄Cl and NaHCO₃ are lifted up by means of a scew pumpsuch as an Archimedes screw (51) being driven by a motor (50), to anoutlet (76) from said precipitator (22) to a refining processingcompartment (60).
 15. The method of claim 1, wherein limestone, Ca(OH)₂,is fed into a process unit (20) for regenerating ammonia, NH₃, theammonia further being guided to said mixing unit (32) via a pipe (19)for mixing with additional NH₃ (2), so as to mix salt water and ammonia(2, 19) and pump said mixture of NH₄OH into said feed pipe (67) in saidprocess unit (17).
 16. A method according to claim 1, wherein said gasturbine (7) drives a generator (9) and a steam driven generator (31) forgenerating electrical energy which is partially exported as energy (15)and partially used for pumping work, gas and CO₂ export work, andheating of H₂O in a process unit (24) that precipitates soda/Na2CO3 (12)for export, and CO₂ and fresh water which is exported or partly returnedto the process.
 17. A process unit (17) for removing CO₂ from an exhaust(77) from a combustion engine or gas turbine (7), comprising thefollowing features: an inlet (35 a) with a fan (35 b) and an outlet (79a) for exhaust (13) of reduced CO₂ content; in which cooled salt water(30) is piped into said process unit (17) via an upper swivel (40)having vanes for rotating a coaxial pipe (67), said coaxial pipe (67)for seawater and NH₄OH feed, said coaxial feed pipe (67) being arrangedpreferably in a centre line of said process unit (17); in which NH₄OH isguided in via a lower swivel (46) on said coaxial pipe (67) and mixedwith said cooled salt water (30) and released via a series of nozzles(42) from said feed pipe (67), said nozzles (42) arranged in severalvertical levels, to upwardly flowing and rotating exhaust (77) of saidprocess unit (17); thus achieving a mixture of NH₄OH-containing saltwater and CO₂-rich exhaust (77) for formation of NaHCO₃, NH₄Cl anddesalinated water.
 18. The process unit of claim 17, wherein saidprocess unit (17) has an increasing diametre with increasing elevationfrom said lower inlet (35 a) to said upper outlet (79 a), and withdraining guide gutters (38) to drains (43) leading to outlets (45) andfurther to a collector tank (48) for the process unit's (17) productsNaHCO₃, NH₄Cl and fresh water.
 19. The process unit of claim 17, whereinsaid rotation direction of said exhaust (77) and said rotation directionof said coaxial feed pipe (67) are opposite in order to increase adegree of mixing between exhaust (77) and added fluid (30, 47).
 20. Theprocess unit of claim 17, wherein NH₄OH enters through said lower swivel(46) to a central, coaxial inner pipe (47) in said coaxial feed pipe(67), said inner pipe (47) being surrounded by a mantle of salt water(30) and in which inner pipe (47) NH₄OH is guided out through pipes (69)to seawater ring nozzles (42) of said feed pipe (67), for mixing ofNH₄OH and seawater in said nozzles (42) during flushing of said NH₄OHand said seawater from said nozzles (42), so as to change said exhaust(77) which gradually changes to CO₂-lean exhaust (13).
 21. A method fordesalinating salt water (5), and for removing CO₂ from a CO₂-richexhaust (77) from a combustion engine or gas turbine (7), comprising thefollowing steps: liquefied natural gas, LNG (4), is fed into a heatexchanger (6) in which said LNG (4) receives heat from combustion air(3) from the atmosphere, said combustion air being provided via a line(28) to an air inlet (33) of said gas turbine (7); said heat exchanger(6) evaporating said LNG (4) to gaseous form (29), said gas (29) beingguided to a fuel gas skid (8) for supplying fuel to said gas turbine(7); in which said combustion air (3, 28) which, at said air inlet (33)to said gas turbine, has a lowered temperature relative to said air (3)before said heat exchanger (6), and thus increases the efficiency ofsaid gas turbine (7); in which CO₂-rich exhaust (77) from said gasturbine (7) is guided into a process unit (17) having an inlet (35 a)with a fan (35 b) and an outlet (79 a) for exhaust (13) of reduced CO₂content; in which said salt water (5, 30) is guided into said processunit (17), via a coaxial feed pipe (67) for seawater and NH₄OH feed; andinto which NH₄OH is guided via said coaxial feed pipe (67) and mixedwith said cooled salt water (30) and released from said coaxial feedpipe (67) to flowing exhaust (13) of said process unit (17); thusachieving a mixture of NH₄OH-containing salt water and CO₂-rich exhaust(77) for removing CO₂ from said exhaust (77), thereby producing saidCO₂-lean exhaust (13) and fresh water.
 22. The method of claim 21,wherein said LNG (4) in said heat exchanger (6) also receives heat fromsaid salt water (5) that becomes cooled salt water (30), said cooledsalt water (30) from said heat exchanger (6) is guided into said processunit (17) via said coaxial feed pipe (67) for seawater and NH₄OH feed.23. The method of claim 22, said coaxial feed pipe (67) being arrangedin a centre line of said process unit (17).
 24. The method of claim 21,wherein said salt water (5, 30) is fed into said coaxial feed pipe (67)via an upper swivel (40) having rotation vanes for rotating said coaxialpipe (67).
 25. The method of claim 21, wherein NH₄OH is guided via alower swivel (46) on said coaxial feed pipe (67) and mixed with saidcooled salt water (30) and released from said coaxial feed pipe (67) viaa series of nozzles (42) arranged in several vertical levels, toupwardly flowing and rotating exhaust (13) of said process unit (17);26. The method of claim 21, wherein said LNG (4) in said heat exchanger(6) also receives heat from steam (27) generated from a steam turbine(31).
 27. The method of claim 21, wherein said heat exchanger (6)evaporating said LNG (4) to gaseous form (29), said gas (29) beingguided to a gas export module (10).
 28. The method according to claim21, wherein the exhaust flow through said process unit (17) is providedan increasing diametre with increasing elevation from said lower inlet(35 a) to said upper outlet (79 a), and with draining guide gutters (38)to drains (43) leading to outlets (45) and further to a collector tank(48) for the process unit's (17) products NaHCO₃, NH₄Cl and H₂O.
 29. Themethod according to claim 21, said salt water (5) preferably beingseawater.
 30. The method according to claim 21, said process resultingin the formation of NaHCO₃, NH₄Cl and fresh water.
 31. A method fordesalinating salt water (5) and removing CO₂ from a CO₂-rich exhaust(77) from a combustion engine or gas turbine (7), comprising thefollowing steps: LNG (4) is fed into a heat exchanger (6) in which saidLNG (4) receives heat from said salt water (5) that becomes cooled saltwater (30), and for evaporating said LNG (4) to gas (29) being guided toa fuel gas skid (8) for supplying fuel to said gas turbine (7); saidCO₂-rich exhaust (77) from said gas tubine (7) is guided into a processunit (17) having an inlet (35 a) with a fan (35 b) and an outlet (79 a)for CO₂ reduced exhaust (13); said cooled salt water (30) from said heatexchanger (6) is guided into said process unit (17) having a feed pipe(67) for seawater and NH₄OH, said feed pipe having nozzles inside saidprocess unit (17); in which NH₄OH is fed through said feed pipe (67) andmixed with said cooled salt water (30) and released from said feed pipe(67) to said process unit's (17) through flowing CO₂-containing exhaust(77); thus achieving a mixture of NH₄OH-containing salt water and saidCO₂-rich exhaust (77), for formation of fresh water and releasing saidCO₂-reduced exhaust (13) to the atmosphere.
 32. The method of claim 31,wherein, in addition to formation of fresh water, NaHCO₃ and NH₄Cl areformed in said process unit (17).
 33. The method of claim 31, whereinsaid LNG (4) in said heat exchanger (6) receives heat from steam (27)from a steam turbine (31).
 34. The method of claim 31, wherein said heatexchanger (6) is evaporating said LNG (4) to gas (29) that partially isguided to a gas export module (10).
 35. The method of claim 31, whereinsaid LNG (4) in said heat exchanger (6) receives heat from combustionair (3) which thus is cooled and fed via a line (28) to an air inlet(33) to said gas turbine (7),
 36. The method of claim 35, wherein saidcombustion air (3, 28) which, at said air inlet (33) to said gasturbine, has a lowered temperature due to giving heat to said LNG (4) onits way through said heat exchanger (6), and thus becomes more dense andthus increases the efficiency for said gas turbine (7);
 37. The methodof claim 31, wherein said feed pipe (67) being coaxial and arrangedpreferably in a centre line of said process unit (17).
 38. The method ofclaim 31, wherein NH₄OH is guided in via a lower swivel (46) on saidfeed pipe (67) and mixed with said cooled salt water (30) and releasedvia a series of nozzles (42) in several vertical levels from said feedpipe (67) to said process unit's upward flowing, rotating exhaust (13);